Method and System for Improving Performance in Discovery Stage of Fast Roaming

ABSTRACT

The present disclosure discloses a method and digital device for improving performance in discovery stage of fast roaming. A disclosed digital device switches from a first wireless communication channel to a second wireless communication channel; transmits, on the second wireless communication channel, a request message comprising a designated field; and switches from the second wireless communication channel to the first wireless communication channel prior to receiving a response message corresponding to the request message on the second wireless communication channel. A network device receives the request message from a client device on the second wireless communication channel. The request message is associated with a first signal strength level. The network device determines that the request message includes a designated field; and transmits a response message to the client device via a different communication interface, such as a wired or wireless distribution system, or the client device&#39;s data transmission channel.

FIELD

The present disclosure relates to wireless fast roaming in wirelessnetworks. In particular, the present disclosure relates to improvingperformance in discovery stage of fast roaming in wireless networks.

BACKGROUND

Wireless digital networks, such as networks operating under the currentElectrical and Electronics Engineers (IEEE) 802.11 standards, arespreading in their popularity and availability. With such popularity,however, problems related to fast roaming tend to occur during highspeed movement of a client device in a wireless network.

When a client device moves at a low speed in the wireless network, theclient device can iteratively scan through a plurality of wirelesschannels and determine which network device to associate with.Specifically, the client device can send a request message, such as aprobe request, and receive a response message, such as a probe response,from a network device in the neighborhood. Because the speed of clientmovement is rather slow, the change in location among multipleiterations typically does not cause the signal strength level (e.g.,received signal strength indication, RSSI) to vary drastically, andthereby will not likely affect the accuracy of the scanning procedure.

Nevertheless, when a client device moves at a high speed in the wirelessnetwork, the change in location among multiple iterations of scanningcan be so large that it causes the signal strength level (e.g., RSSI) tovary drastically, and thereby affects the accuracy of scanning. Hence,in order to ensure the accuracy of scanning when a client device movesat a high speed, the client device needs to reduce the scanningintervals. As a result, the client device will spend less time on datatransmissions and more time on network device discovery when moving at afast speed. Thus, network traffic could suffer apparent degradationand/or fluctuation.

Conventionally, a network device can maintain a list of adjacent networkdevices and the wireless channels that they communication on, and sendthe list to a client device when the client device needs to roam at ahigh speed. Thus, the client device uses the adjacent network devicelist it received from the network device that it currently is associatedwith to reduce the number of channels the client device needs to scan.However, because the adjacent network device list may not be up-to-dateor complete, the conventional solution to channel scanning during fastroaming may not produce accurate results.

Moreover, the solution does not benefit much in a high densitydeployment of wireless network devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be best understood by referring to thefollowing description and accompanying drawings that are used toillustrate embodiments of the present disclosure.

FIG. 1 is a diagram illustrating an exemplary wireless networkenvironment according to embodiments of the present disclosure.

FIG. 2A is a diagram illustrating an exemplary scanning mechanism indiscovery stage of fast roaming in a wireless network according toembodiments of the present disclosure.

FIG. 2B is a sequence diagram illustrating an exemplary scanningmechanism in discovery stage of fast roaming in a wireless networkaccording to embodiments of the present disclosure.

FIG. 3 illustrates an exemplary wireless communications in discoverystage of fast roaming in a wireless network according to embodiments ofthe present disclosure.

FIG. 4 illustrates exemplary wireless communications in discovery stageof fast roaming in a wireless network according to embodiments of thepresent disclosure.

FIG. 5 illustrates an exemplary network frame used in discovery stage offast roaming in a wireless network according to embodiments of thepresent disclosure.

FIGS. 6A-6B illustrate exemplary device location tracking used indiscovery stage of fast roaming according to embodiments of the presentdisclosure.

FIGS. 7A-7B are flowcharts illustrating exemplary process of channelscanning in discovery stage of fast roaming in a wireless networkaccording to embodiments of the present disclosure.

FIG. 8 is a block diagram illustrating exemplary system for channelscanning in discovery stage of fast roaming in a wireless networkaccording to embodiments of the present disclosure.

FIG. 9 is a block diagram illustrating exemplary system for channelscanning in discovery stage of fast roaming in a wireless networkaccording to embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following description, several specific details are presented toprovide a thorough understanding. While the context of the disclosure isdirected to channel scanning in discovery stage of fast roaming inwireless network, one skilled in the relevant art will recognize,however, that the concepts and techniques disclosed herein can bepracticed without one or more of the specific details, or in combinationwith other components, etc. In other instances, well-knownimplementations or operations are not shown or described in details toavoid obscuring aspects of various examples disclosed herein. It shouldbe understood that this disclosure covers all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent disclosure.

Overview

Embodiments of the present disclosure relate to wireless fast roaming inwireless networks. In particular, the present disclosure relates toimproving performance in discovery stage of fast roaming in wirelessnetworks.

According to embodiments of the present disclosure, a digital device canreduce or eliminate the waiting periods on wireless channels during thescanning procedure. As a result, the digital device can increase thedata transmission periods on the current channel that the digital deviceuses for communication with a network device (e.g., an access point,AP).

With the solution provided herein, a disclosed digital device switchesfrom a first wireless communication channel to a second wirelesscommunication channel; transmits, on the second wireless communicationchannel, a request message comprising a designated field; and switchesfrom the second wireless communication channel to the first wirelesscommunication channel prior to receiving a response messagecorresponding to the request message on the second wirelesscommunication channel.

Furthermore, a disclosed network device receives the request messagefrom a client device on the second wireless communication channel. Therequest message is associated with a first signal strength level. Thenetwork device determines that the request message includes a designatedfield; and transmits a response message to the client device via adifferent communication interface, such as a wired or wireless interfaceto a distribution system or the client device's data transmissionchannel.

Additionally, in some embodiments, the client device can selectivelyreduce the number of wireless communication channels to be scannedduring the discovery stage of fast roaming based at least on thelocation tracking information associated with the neighboring networkdevices and the client device.

Computing Environment

FIG. 1 shows an exemplary wireless digital network environment accordingto embodiments of the present disclosure. FIG. 1 includes a controller100 and/or a switch 110 that connect to a plurality of network devices,such as access points AP1 120, AP2 130, and AP3 140 in a wirelessnetwork. Moreover, a network device may be connected to one or moreclient devices via wireless or wired connections. For example, asillustrated in FIG. 1, AP1 120 is connected to client device 150 viawireless connections.

Note that, some client devices may be moving from one location to adifferent location in the wireless network. The speed of movement can behigh for some client devices under some occasions, and can be low underother occasions or for other client devices. As client device 150 moves,client device 150 may change its association from one network device toanother. For example, initially, client device may be associated withaccess point AP1 120. As client device 150 moves along the illustratedpath, client device 150 may become disassociated with AP1 120, and startto associate with AP2 130. When client device 150 moves farther awayfrom AP2 130, client device 150 may disassociate with AP2 130 and startto associate with AP3 140, etc.

The network depicted in FIG. 1 may operate on a private networkincluding one or more local area networks. The local area networks maybe adapted to allow wireless access, thereby operating as a wirelesslocal area network (WLAN). In some embodiments, each network correspondsto a unique basic service set (BSS) identifier. In some embodiments, oneor more networks may share the same extended service set (ESS).

In addition, network depicted in FIG. 1 may include multiple networkcontrol plane devices, such as network controller 100. Network controlplane device can optionally provide functions, such as creating andenforcing network policies, providing adaptive radio management,intrusion prevention, quality of service, and/or mobility, etc.

Before client device 150 starts to associate with a network device,client device 150 typically must go through a channel scanning processto discovery network devices located within its current neighborhood.The channel scanning mechanism for discovery stage is described in thenext section.

Channel Scanning Mechanism

FIG. 2A illustrates an exemplary scanning mechanism in discovery stageof fast roaming in a wireless network. The axis in FIG. 2A indicatestime 200. As shown in FIG. 2A, the scanning mechanism of a client deviceperforms multiple iterations of scanning activities, including scanningiteration 230, scanning iteration 235, etc. After completing eachscanning iteration, the client device waits for a period of intervalsbefore starting another scanning iteration. For example, aftercompleting scanning iteration 230, the client device waits for a periodof time as configured by scanning interval 212 before starting scanningiteration 235. During the scanning intervals, the client device maycontinue data transmission with the network device it currentlyassociates with.

In addition, each scanning iteration may include multiple scanningperiods separated by scanning intervals. For example, scanning iteration230 includes scanning period 220 and scanning period 222, as well asscanning interval 210 between scanning periods 220 and 222. Also,scanning iteration 235 includes scanning period 224 and scanning period226, as well as scanning interval 214 between scanning periods 224 and226. During the scanning intervals 210 and 214, the client device maycontinue data transmission with the network device it currentlyassociates with and on the wireless communication channel that thenetwork device uses.

During each scanning period, such as scanning periods 220, 222, 224, and226, the client device switches from a first channel (e.g., CH1 240) toa second channel (e.g., CH2 241), to a third channel (e.g., CH3 242), toa fourth channel (e.g., CH4 243), to a fifth channel (e.g., CH5 244), toa sixth channel (e.g., CH6 245), etc. In some embodiments, after theclient device switches to a channel, the client device sends one or morerequest messages, such as a probe request, on the channel. Then, theclient device listens for one or more response messages, such as a proberesponse, on the channel for a predetermined period of time. After thepredetermined period of time expires, the client device switches to thenext channel, and repeat the process. During each scanning period, theclient device will scan through each channel at least once. If theclient device does not receive any response message on a particularchannel in a previous scanning period (e.g., scanning period 220), theclient device may receive a response message on the particular channelin another scanning period (e.g., scanning period 222, scanning period224, etc.), whereas the response message was sent in response to arequest message from the client device in the previous scanning period(e.g., scanning period 220).

If when a response message is received by the client device, an extendedperiod of time has elapsed since the request message was sent, theresponse message may not be up-to-date, especially in the scenarioswhere the client device has moved to a different location that is faraway from its original location during the extended period of time. Notethat, the scanning intervals within each scanning iteration (e.g.,scanning interval 210 and scanning interval 214) are typically muchshorter than the scanning intervals between two scanning iterations(e.g., scanning interval 212). Thus, if a request message is sent duringa scanning iteration, and the response message is received during thenext scanning iteration and the client device has been moving at a fastspeed during the two scanning iterations, it is more likely that theresponse message is already out-of-date when received by the clientdevice.

In some embodiments, the lengths of scanning intervals (e.g., scanningintervals 210, 212, and 214) can be configured by a networkadministrator. Therefore, one way to mitigate the problem is to reducethe scanning intervals between the scanning iterations based on theclient device's speed of movement. For example, scanning interval 212may be set to 30 milliseconds when the client device moves at a speed of60 kilometer/hour, and 20 milliseconds when the client device moves at aspeed of 100 kilometer/hour.

FIG. 2B is a sequence diagram illustrating exemplary scanning mechanismin discovery stage of fast roaming in a wireless network according toembodiments of the present disclosure. Specifically, FIG. 2B includesclient device 250, home access point (AP) 252 that client device 250 isassociated with, and other APs in the neighborhood such as AP1 254 andAP2 256.

In the example illustrated in FIG. 2B, at time point t₁, client device250 is in data transmission period 270, during which data transmission280 is performed between client device 250 and home AP 252. As clientdevices 250 changes its physical location, it may need to discoveranother AP in the neighborhood that provides stronger coverage and/orbetter service than home AP 252. Thus, at time point t₂, client device250 starts the channel scanning process, and performs channel switch 272to switch to a first wireless communication channel (e.g. channel 1).Next, at time point t₃, client device 250 sends a request message (e.g.,probe request 282) on the first wireless communication channel. In theillustrated example, it is assumed that AP1 254 communicates on channel2 and AP2 256 communicates on channel 1. Thus, AP1 254 will not receivethe request message sent on channel 1, but AP2 256 receives the requestmessage (e.g., probe request 282) at time point t₄. For illustrationpurpose only, assuming that AP2 256 sends a response message (e.g.,probe response 284) at time point t₅ in response to the request message,and the response message is received by client device 250 at time pointt₆. At time point t₇, client device 250 switches to a second wirelesscommunication channel, e.g., channel 2. The time period between channelswitch 272 at time point t₂ and channel switch 276 at time point t₇indicates client device 250's waiting period 274 on channel 1.

Likewise, after client device 250 switches to the second wirelesscommunication channel, client device 250 sends another request message(e.g., probe request 286) on the second wireless communication channel(e.g., channel 2) at time point t₈. Because AP1 254 communicates onchannel 2, AP1 254 will receive the request message (e.g., probe request286) at time point t₉. Subsequently, AP1 254 sends a response message(e.g., probe response 288) at time point t₁₀. The response message isreceived by client device 250 at time point t₁₁. Later, client device250 switches to a third wireless communication channel at time pointt₁₂. The time period between channel switch 276 at time point t₇ andchannel switch 279 at time point t₁₂ indicates client device 250'swaiting period 276 on channel 2. In some embodiments, the waiting periodon each channel (e.g., waiting period 274 and waiting period 276) variesfrom 20 milliseconds to 40 milliseconds on each channel.

Alternative Communication Exchanges During Discovery Stage

FIG. 3 illustrates an alternative exemplary wireless network environmentaccording to embodiments of the present disclosure. FIG. 3 includes acontroller 300 and/or a switch 310 that connect to a plurality ofnetwork devices, such as access points home AP 320 and target AP 325 ina wireless network. Moreover, home AP 320 is currently connected toclient device 330 via wireless connections. Furthermore, target AP 325is in the neighborhood of client device 330, and is a potential AP thatclient device 330 may become associated with to achieve better coverageand/or service.

In some embodiments, when client device 330 is in discovery stage ofroaming, client device 330 switches to a first wireless communicationchannel, and sends a request message (e.g., a proxy probe request 340)on the first wireless communication channel. If target AP 325 alsocommunicates on the first wireless communication channel, target AP 325will receive the request message, and sends a response message (e.g.,proxy probe response 350) through a wired interface, e.g., over adistribution system and/or on client device 330's working channel.Subsequently, home AP 320 forwards the response message (e.g., proxyprobe response 355) to client 330. As a result, it is not necessary forclient device 330 to wait on the first wireless communication channelfor the response message. Thus, client device 330 can switch back to thewireless communication channel it uses to communicate with home AP 330,and resume data transmissions with the home AP 320. In some embodiments,the waiting period on each channel can be set to merely 1 to 2milliseconds, and thus dramatically reducing the interruption of datatransmissions between client device 330 and home AP 320 during discoverystage of fast roaming.

In some embodiments, after client 330 roams to another AP (e.g., AP2,not shown) other than target AP 325, AP2 will send a notificationmessage (e.g., IAPP-ADD-notify in accordance with IEEE 802.11f standard)and a layer 2 update frame. After home AP 320 is notified that client330 has roamed to another AP (e.g., AP2), home AP 320 will drop theresponse message received from target AP 325 (e.g., proxy probe response350). Note that, after layer 2 frame update frame is transmitted, lay 2transfer table will be updated. Hence, subsequent proxy probe responseframes directed to client 330 will be sent to the other AP (e.g., AP2).Alternatively, in some embodiments, home AP 320 may decide to drop proxyprobe response frames after a pre-determined number of failedretransmissions, and thus avoiding excessive load on home AP 320.

FIG. 4 illustrates exemplary wireless communications in discovery stageof fast roaming in a wireless network. Specifically, FIG. 4 includesclient 410 and multiple access points, including home AP 422, AP1 424,and AP2 426, etc. In this example, home AP 422 is currently connected toclient device 410 via wireless connections. Furthermore, AP1 424 and AP2426 are also in the neighborhood of client device 410, and thuspotential APs that client device 410 may become associated with, e.g.,after roaming to a new location.

In some embodiments, client device 410 initially communicates with homeAP 422 on a wireless communication channel. At time point t₁, clientdevice 410 is in data transmission period 460, during which datatransmission 440 is performed between client device 410 and home AP 422.

As client devices 410 changes its physical location, it may need todiscover another AP in the neighborhood that provides stronger coverageand/or better service than home AP 422. Thus, at time point t₂, clientdevice 410 starts the channel scanning process, and performs channelswitch 432 to switch to another wireless communication channel (e.g.channel 1) at time point t₂. After client device 410 switches to theother wireless communication channel, client device 410 sends a requestmessage (e.g., a proxy probe request 450) on the other wirelesscommunication channel at time point t₃, and immediately performs achannel switch 434 back to the initial wireless communication channel,which client device 410 uses to communicate with home AP 422, at timepoint t₄. Thereafter, client device 410 resumes data transmission 444with home AP 422, e.g., at time point t₈ until client device 410performs another channel switch 436 to scan the next wirelesscommunication channel at time point t₁₀.

Accordingly, the time period between channel switch 432 at time point t₂and channel switch 434 at time point t₄ indicates scanning period 470 onthe other wireless communication channel, e.g., channel 1. Moreover, thetime period between channel switch 434 at time point t₄ and channelswitch 436 at time point t₁₀ indicates the increased data transmissiontime period 464 compared to other alternatives.

On the other hand, after an access point (e.g., AP2 426) receives arequest message (e.g., proxy probe request 450) at time point t₅, theaccess point will send a response message, e.g., proxy probe response452 at time point t₆. In some embodiments, the access point (e.g., AP2426) can send the response message over a wired interface, e.g., over adistributed system. In other embodiments, the access point (e.g., AP2426) can send the response message via wireless distribute system (e.g.mesh networks). In the illustrated example, assuming that AP2 426 sendsthe response message via wired interface to client device 410. Theresponse message, e.g., proxy probe response 452, which has adestination address associated with client device 410, is first receivedby home AP 422. Because client device 410 is currently associated withhome AP 422, all messages with a destination address associated withclient device 410 will be transmitted to client device 410 via home AP422. After home AP 422 receives the response message (e.g., proxy proberesponse 452) at time point t₇, home AP 422 will forward the responsemessage (e.g., forwarded proxy response 453) to client device 410 attime point t₈. The forwarded response message reaches client device 410at time point t₉ on the initial wireless communication channel.

Thereafter, at time point t₁₀, client device 410 performs channel switch436 to switch to the next wireless communication channel, e.g., channel2, and sends another request message, e.g., proxy probe request 454,which is received by AP1 424 at time point t₁₂. After sending therequest message on the next wireless communication channel (e.g.,channel 2), client device 410 performs channel switch 438 to switch backto its initial communication channel immediately at time point t₁₁.

Similar to the scanning of the previous channel, after an access point(e.g., AP1 424) receives a request message (e.g., proxy probe request454) at time point t₁₂, the access point will send a response message,e.g., proxy probe response 456 at time point t₁₃. In some embodiments,the access point (e.g., AP1 424) can send the response message over awired interface, e.g., over a distributed system. In other embodiments,the access point (e.g., AP1 424) can send the response message viawireless distribute system (e.g. mesh networks).

Assuming that AP1 426 sends the response message via wired interface toclient device 410. The response message (e.g., proxy probe response456), which has a destination address associated with client device 410,is first received by home AP 422. After home AP 422 receives theresponse message (e.g., proxy probe response 456) at time point t₁₄,home AP 422 will forward the response message (e.g., forwarded proxyresponse 457) to client device 410 at time point t₁₅. The forwardedresponse message reaches client device 410 at time point t₁₆ on theinitial wireless communication channel.

Accordingly, the time period between channel switch 436 at time pointt₁₀ and channel switch 438 at time point t₁₁ indicates scanning period472 on the next wireless communication channel, e.g., channel 2.Moreover, the time period subsequent to channel switch 438 at time pointt₁₁ corresponds to the increased data transmission time period 468compared to other alternatives.

Note that, if client device 410 receives a response message (e.g., proxyprobe response 453 or proxy probe response 457) through a wiredinterface, such as via a distribution system, client device 410 furthercalculates a signal strength level associated with the sender of theresponse message (e.g., a Received Signal Strength Indicator (RSSI)level associated with AP2 426 or AP1 424) through the following formula:

RSSI_(AP)=RSSI_(sta) +TxPower_(sta) −TxPower_(ap)

Here, RSSI_(sta) indicates a signal strength level associated with therequest message (e.g., proxy probe request 450 or 454) from clientdevice 410 as received by a network device (e.g., AP 2 426 or AP1 424)in the wireless network. TxPower_(sta) indicates the transmit powerlevel of client device 410 that sends the request message, whereasTxPower_(ap) indicates the transmit power level of the network device(e.g., AP2 426 or AP1 424) that sends the response message.

In some embodiments, client device 410 and network devices (e.g., AP1424 or AP2 426) transmit at the same or similar power setting. Thus, thesignal strength of a message from client device 410 as received by thenetwork devices will be same or similar to the signal strength of amessage from the network devices as received by client device 410.

In other embodiments, client device 410 and network devices (e.g., AP1424 or AP2 426) transmit at the different power settings. Accordingly,the signal strength of a message from client device 410 as received bythe network devices neither will be same nor similar to the signalstrength of a message from the network devices as received by clientdevice 410. Therefore, adjustment of signal strength level needs to becalculated in order to correctly estimate the signal strength that wouldbe associated with a response message transmitted from an network deviceon the network device's working channel (e.g., from AP2 426 on channel1), if the response message were to be sent to client device 410directly from the network device (e.g., AP2 426) on the network device'sworking channel (e.g., channel 1). As shown above, the adjustment iscalculated based on the difference between transmit power settings ofclient device 410 and the network device (e.g., AP2 426).

Note that the response message (e.g., proxy probe response 452) can betransmitted through two ways. In some embodiments, the response messagecan be transmitted via a distribute system, which may be a wiredinterface or a wireless interface to backhaul communication channels. Ifthe response message is transmitted via the distribution system, theresponse message can be encapsulated as FIG. 5 format. In otherembodiments, the response message is transmitted over the air on theclient device's working channel. If the response message is transmittedon the client device's working channel, the response message may be in aprobe response format in compliance with IEEE 802.11 standard.

Also, it is important to note that, because the network device (e.g.,AP2 426) is allowed to send a response message (e.g., proxy proberesponse 452) through a wired ore wireless interface over a distributionsystem and/or on client device 410's working channel, it is notnecessary for client device 410 to wait on each wireless communicationchannel for the response message during channel scanning in thediscovery stage of fast roaming. Thus, client device 410 can switch backto the wireless communication channel it uses to communicate with homeAP 410 immediately after sending a request message (e.g., a proberequest) on the channel to be scanned, and resume data transmissionswith the home AP 422. In some embodiments, the waiting period on eachchannel can be set to merely 1 to 2 milliseconds, and thus significantlyimprove data transmissions between client device 410 and home AP 422during discovery stage of fast roaming.

Network Response Frame Format

FIG. 5 illustrates an exemplary network frame used in discovery stage offast roaming in a wireless network. FIG. 5 includes at least thefollowing fields: source address (SA) 520, destination address (DA) 540,special information element (IE) field 560 indicating that the networkframe may require special processing, and payload 580. In the givenexample, when used in a response message, the special value “88BF” isused to indicate that the network response frame requires specialprocessing, for example, because it is sent over a distributed systemrather than on the network device's working channel. In one embodiment,special IE field 560 may indicate a prototype field. If specialprocessing is required, the response message may be encapsulated with anEthernet header with prototype field value set to, for example, “88BF.”

On the other hand, in a request message, the same special value “88BF”can be used in the header of the request message to indicate that theclient device sending the request has the capability of performing thealternative channel scanning protocol. In addition, a client devicesupporting the alternative channel scanning protocol typically shouldeither include this proto-type code information element in itsassociation response message, probe request message, beacon frame, etc.,or encapsulate the message with an Ethernet header with proto-type setto “88bf.” Network devices supporting this alternative channel scanningprotocol typically should include this information element in theirprobe response messages, association response messages, beacon frames,etc.

Furthermore, in some embodiment, network frames can optionally include afield indicating a peer node's signal strength level, e.g., a RSSIvalue. The signal strength level can be indicated in the header or thebody of the network message. For example, an access point may includethe RSSI of a request message received from the client device in a proberesponse message to the client device.

Moreover, network frames can also include a timestamp, which can be usedto check the validity of the response messages. The scan timestampelement can be added to a probe request message if the client devicesending the message supports the alternative channel scanning mechanism.Also, the scan timestamp element can be added to a probe responsemessage if the access point sending the response supports thealternative channel scanning mechanism.

Specifically, a client device can add its local time to the proberequest message during channel scanning. After a target access point(target AP) receives the probe request including the scan timestamp, thetarget AP may copy the timestamp to its probe response message, which issent to the client device via a distributed system. When the clientdevice receives the forwarded probe response message from its home AP,the client device first checks the timestamp against its current localtime prior to processing the message. If the difference between the scantimestamp included in the response message and the current local time atthe client device exceeds a predetermined threshold, the device willdetermine that the response message is not a valid response because itis out-of-date, and ignore the response message.

Client Device Location Tracking in Discovery Stage of Fast Roaming

In some embodiments, a network device (e.g., an access point) candiscover its neighboring network devices in a wireless network, andbroadcast its neighborhood information, such as the location, thechannel, the transmit power, and/or the antenna gain of its neighboringnetwork devices in beacon frames transmitted over the air. This allows aclient device, which is in the discovery stage of fast roaming, toobtain a plurality of candidate network devices through analyzing thebeacon frame. In some embodiments, the client device can further get itsown physical location, e.g., through a global positioning system (GPS)module. By comparing the client device's physical location against theneighborhood information in the beacon frame sent by the network device,the client device and/or a network device can identify one or moresuitable network devices in the neighborhood as potential target accesspoints for fast roaming.

FIGS. 6A-6B illustrate exemplary device location tracking used indiscovery stage of fast roaming. FIG. 6A includes at least a field fornetwork device identifiers (e.g., AP 620) and a field for network devicelocations (e.g., AP location 640). In the illustrated example, assumingthat AP1 622 is located at (40°7′00, 116°35′00), AP2 624 is located at(40°7′30, 116°35′20), AP3 626 is located at (40°7′30, 116°35′50), etc.FIG. 6B includes at least a field for client device identifiers (e.g.client 660) and a field for client device locations (e.g., clientlocation 680). In the illustrated example, assuming that client1 662 islocated at (40°7′20, 116°36′30). Note that, the information in FIGS. 6Aand 6B used for client location tracking can be maintained on a clientdevice, a network device, or an external storage device that isaccessible by the client device and/or the network device. The networkdevices' locations may be stored in the same or different storagestructure as the client device(s)' location(s).

Based on the location tracking information in FIG. 6A and/or FIG. 6B, aclient device and/or a network device may identify the closest networkdevices to the client's current location. In some embodiments, FIG. 6Bmay also include the client device's anticipated location after fastroaming starts. In that case, the client device and/or the networkdevice can proactively determines which access points will be located inthe neighborhood where the client device is about to move into.

In some embodiments, the client device and/or network device may use thefollowing formulas to identify the neighboring access points. First, theclient device and/or the network device calculate a distance between theclient device and an access point based on their physical locations. Forexample, when GPS coordinates are available for the client device andthe access points, the distance between the two devices can bedetermined by:

D=func(lattitude_(sta),longitude_(sta),lattitude_(ap),longitude_(ap))  (1)

Because the distance between the access point and the client device isfar shorter than the radius of earth, the above formula can besimplified as:

D=√{square root over (D _(latitude) ² +D _(longitude) ²)}  (2)

D _(longitude)=R×cos(latitude_(ap))×|longitude_(ap)−longitude_(sta)|  (3)

D _(latitude) =R×|latitude_(ap)−latitude_(sta)|  (4)

where R indicates the radius of the earth.

The following formula can be used to calculate the free space lossbetween the client device and the access point:

Loss=32.44+20lgF (Mhz)+20lgD (Km)  (5)

The received signal strength of the access point can be calculated by:

RSSI=tx_power+tx_ant_gain−Loss+rx_ant_gain−noise_floor  (6)

In some embodiments, a client device may determine that it is time toinitiate roaming if the signal strength levels (e.g., one or more RSSIvalues) of messages, which are received from the access point that theclient device is currently associated with, are lower than apredetermined threshold or lower than a signal strength level associatedwith a different message received from another access point in thenetwork. In one embodiment, the client device may select an accesspoint, the message transmitted from which are associated with thehighest signal strength levels, to be the target AP. In someembodiments, the fluctuation in signal strength levels may be caused bytemporary or permanent physical obstruction. Also, there may be variousdegrees of difference between the calculated signal strength value andthe actual signal strength value. Therefore, the client device may needto perform another round of check and calculation of the signal strengthlevel during the next scanning period and/or iteration.

In some embodiments, if a client device and/or network device identifyone or more neighboring network devices as target APs, the client devicewill selectively scan through the channels that those target APs use tocommunication, rather than iteratively scan through each and everywireless communication channel during the discovery stage of fastroaming.

Processes for Improving Performance in Discovery Stage of Fast Roaming

FIG. 7A is a flowchart illustrating exemplary process of channelscanning at a network device supporting the specific channel scanningmechanism in discovery stage of fast roaming in a wireless network.During operations, a network device receives a request message from aclient device over a wireless communication channel (operation 710). Insome embodiments, the wireless communication channel is the currentworking channel of the network device. The request message may include,for example, an association request, a probe request, etc.

Next, the network device determines whether the request message includesan information element (IE) indicating that the client device supports aspecific channel scanning mechanism (operation 720). In someembodiments, the specific channel scanning mechanism allows the clientdevice to switch back immediately to its working data transmissionchannel after sending the request message on the channel to be scanned.

If the request message does not include the specific IE, the networkdevice will transmit a response message to the client device on awireless communication channel, which is usually the network device'sworking communication channel (operation 730).

If, on the other hand, the request message includes the specific IEindicating support for the channel scanning mechanism, the networkdevice may optionally perform calculations described in previoussections to derive a signal strength level associated with a responsemessage that the client would have received if the response message wereto be sent on the network device's working communication channel(operation 740). In some embodiments, the calculation may be performedby the client device. In those scenarios, the network device willinclude the signal strength of the request message received from theclient device, for example, in the content of the payload in itscorresponding response message.

In addition, the network device will include a designated informationelement to indicate that the network device supports the specificchannel scanning mechanism (operation 750). If a client device receivesa response message with the designated information element, the clientdevice will derive the signal strength level based on content in thepayload of the response message rather than using the detected signalstrength associated with the received response message.

Thereafter, the network device will transmit the signal strength levelin the response message to the client device via a wired or wirelessinterface to a distribution system, or through the client device'scurrent data transmission channel (operation 760).

FIG. 7B is a flowchart illustrating exemplary process of channelscanning at a client device supporting the specific channel scanningmechanism in discovery stage of fast roaming in a wireless network.During operations, a client device receives a response message from anetwork device over a wireless communication channel (operation 770). Insome embodiments, the client is currently associated with the networkdevice on the wireless communication channel, and uses the wirelesscommunication channel for data transmissions.

Next, the client device determines whether the network device sendingthe response message supports a specific channel scanning mechanismbased on whether the response message includes an information element(IE) (operation 775). Specifically, the indicated channel scanningmechanism can allow the client device to switch back immediately to itsworking data transmission channel after sending the request message onthe channel to be scanned, and improve data transmission performanceduring discovery stage of fast roaming.

If the response message does not include the specific IE, the clientdevice will determine a signal strength level directly from the signalstrength level associated with the received response message (operation780). If, on the other hand, the response message includes the specificIE, and if the signal strength is not already derived by the networkdevice, the client device may optionally perform calculations describedin previous sections to derive a signal strength level associated with areceived response message that the client would have received if theresponse message were to be sent on the network device's workingwireless communication channel rather than the distribution system(operation 790). Note that, in many cases, the derived signal strengthlevel may be different from the signal strength level associated withthe received response message.

Systems for Improving Performance in Discovery Stage of Fast Roaming

FIG. 8 is a block diagram illustrating a network device system forimproving performance in discovery stage of fast roaming in wirelessnetworks according to embodiments of the present disclosure.

Network device 800 includes at least one or more radio antennas 810capable of either transmitting or receiving radio signals or both, anetwork interface 820 capable of communicating to a wired or wirelessnetwork, a processor 830 capable of processing computing instructions,and a memory 840 capable of storing instructions and data. Moreover,network device 800 further includes a receiving mechanism 850, atransmitting mechanism 860, a determining mechanism 870, and a signalderiving mechanism 880, all of which are coupled to processor 830 andmemory 840 in network device 800. Network device 800 may be used as aclient system, or a server system, or may serve both as a client and aserver in a distributed or a cloud computing environment.

Radio antenna 810 may be any combination of known or conventionalelectrical components for receipt of signaling, including but notlimited to, transistors, capacitors, resistors, multiplexers, wiring,registers, diodes or any other electrical components known or laterbecome known.

Network interface 820 can be any communication interface, which includesbut is not limited to, a modem, token ring interface, Ethernetinterface, wireless IEEE 802.11 interface (e.g., IEEE 802.11n, IEEE802.11ac, etc), cellular wireless interface, satellite transmissioninterface, or any other interface for coupling network devices.

Processor 830 can include one or more microprocessors and/or networkprocessors. Memory 840 can include storage components, such as, DynamicRandom Access Memory (DRAM), Static Random Access Memory (SRAM), etc.

Receiving mechanism 850 generally receives one or more network messagesvia network interface 820 from a distribution system or radio antenna810 from a wireless client over a wireless communication channel. Thereceived network messages may include, but are not limited to, requestsand/or responses, beacon frames, management frames, control path frames,and so on. Each message may comprise one or more data packets, forexample, in the form of IP packets.

In some embodiments, receiving mechanism 850 receives a request message(e.g., an association request, or a probe request) from a client deviceon a wireless communication channel. The wireless communication channelcorresponds to the working channel of the network device. In someembodiments, the request message is associated with a first signalstrength level. In some embodiments, the request message includes adesignated field indicating that the client device sending the requestmessage supports a specific channel scanning mechanism.

Transmitting mechanism 860 generally transmits messages, which include,but are not limited to, requests and/or responses, beacon frames,management frames, control path frames, and so on. In some embodiments,transmitting mechanism 860 transmits a response message via a differentcommunication interface if the request message received by receivingmechanism 850 includes the designated field. The response message mayinclude a signal strength level, which can be the same as the signalstrength level corresponding to the received request message in someembodiments, or a derived signal strength level.

Note that, transmitting mechanism 860 may transmit messages through oneor more of the following interfaces: a wired interface to a distributionsystem, a first wireless interface to a distribution system, and/or awireless interface associated with a data transmission wirelesscommunication channel of the client device.

Determining mechanism 870 generally determines whether a request messageor a response message includes a designated field. The designated fieldindicates capability to support a specific channel scanning mechanismduring a discovery stage of fast roaming in a wireless network. If themessage includes the designated field, transmitting mechanism 860 willtransmit the response message via a different communication interfacefrom the working or data transmission wireless communication channel ofnetwork device 800. Otherwise, transmitting mechanism 860 will transmitthe response message via its current working wireless communicationchannel.

Signal deriving mechanism 880 generally derives a signal strength levelassociated with a response message based on the signal strength levelassociated with the received request message, the transmit powerassociated with the client device sending the request message, and thetransmit power associated with the network device sending the responsemessage. The signal deriving mechanism 880 may include the derivedsignal in the content of payload in a response message that is to betransmitted to the client device, if the request message includes thedesignated field.

Therefore, receiving mechanism 850, transmitting mechanism 860,determining mechanism 870, and signal deriving mechanism 880 oftencollectively operate with each other to improve performance of clientdevices during discovery stage of their fast roaming in wirelessnetworks.

FIG. 9 is a block diagram illustrating a digital device system forimproving performance in discovery stage of fast roaming in wirelessnetworks according to embodiments of the present disclosure.

Digital device 900 includes at least one or more radio antennas 810capable of either transmitting or receiving radio signals or both, aprocessor 920 capable of processing computing instructions, and a memory930 capable of storing instructions and data.

Moreover, digital device 900 further includes a receiving mechanism 940,a transmitting mechanism 950, a determining mechanism 960, a switchingmechanism 970, and a signal deriving mechanism 980, all of which arecoupled to processor 920 and memory 930 in digital device 900. Digitaldevice 900 may be used as a client system, or a server system, or mayserve both as a client and a server in a distributed or a cloudcomputing environment.

Radio antenna 910 may be any combination of known or conventionalelectrical components for receipt of signaling, including but notlimited to, transistors, capacitors, resistors, multiplexers, wiring,registers, diodes or any other electrical components known or laterbecome known. Radio antenna 910 can be compliant with a number ofinterfaces, including but not limited to, wireless IEEE 802.11 interface(e.g., IEEE 802.11n, IEEE 802.11ac, etc), cellular wireless interface,satellite transmission interface, or any other interface for couplingdevices in wireless networks.

Processor 920 can include one or more microprocessors and/or networkprocessors. Memory 930 can include storage components, such as, DynamicRandom Access Memory (DRAM), Static Random Access Memory (SRAM), etc.

Receiving mechanism 940 generally receives one or more network messagesradio antenna 910 from a network device serving as a home access pointover a wireless communication channel. The received network messages mayinclude, but are not limited to, requests and/or responses, beaconframes, management frames, control path frames, and so on. Each messagemay comprise one or more data packets, for example, in the form of IPpackets.

In some embodiments, receiving mechanism 940 receives a response message(e.g., an association response, or a probe response) from a networkdevice (e.g., an access point) via a different communication interfacefrom the working wireless communication channel of the network device.The different communication interface comprises one or more of a wiredinterface to a distribution system, a first wireless interface to adistribution system, and/or a second wireless interface associated witha data transmission wireless communication channel of the digitaldevice.

Transmitting mechanism 950 generally transmits messages, which include,but are not limited to, requests and/or responses, beacon frames,management frames, control path frames, and so on. In some embodiments,transmitting mechanism 950 transmits a request message on the working(or data transmission channel) wireless communication channel of digitaldevice 900. The request message may include a designated field, whichindicates that digital device 900 supports a specific channel scanningmechanism.

Determining mechanism 960 generally determines whether a request messageor a response message includes the designated field. Inclusion of thedesignated field generally indicates capability to support a specificchannel scanning mechanism by a digital device (including networkdevices or client devices) during a discovery stage of fast roaming in awireless network.

If the message does not include the designated field, determiningmechanism 960 will determine the signal strength level directly based onthe signal strength of the response message received from the networkingdevice serving as the home access point.

If the message includes the designated field, signal deriving mechanism980 will derive a signal strength level associated with a responsemessage based on the content of the response message. In someembodiment, signal deriving mechanism 980 may retrieve a derived signalin the content of payload in a response message if it has been derivedby the network device sending the response message to the client device.Alternatively, signal deriving mechanism 980 may retrieve a first signalstrength level from the content of the response message, and derive asecond signal strength level based on the first signal strength levelwhich is associated with a previously request message from the digitaldevice, the transmit power associated with the digital device, and thetransmit power associated with the network device sending the responsemessage.

Further, switching mechanism 970 generally can switch digital device 900from communicating on one wireless communication channel tocommunicating on another wireless communication channel. For example,switching mechanism 970 can switch digital device 900 from its workingchannel used for data transmission with its current home access point toa scanning channel. Also, switching mechanism 970 can switch from onescanning channel to a different scanning channel. In addition, whendigital device 900 supports a specific channel scanning mechanism,switching mechanism 970 can switch back from the scanning channel to itsworking channel used for data transmission with the home AP immediatelyafter transmitting a request message on the scanning channel.

Therefore, receiving mechanism 940, transmitting mechanism 950,determining mechanism 960, switching mechanism 970, and signal derivingmechanism 980 often collectively operate with each other to improveperformance by digital device 900 during discovery stage of its fastroaming in wireless networks.

According to embodiments of the present disclosure, network servicesprovided by wireless network device 800, solely or in combination withother wireless network devices, include, but are not limited to, anInstitute of Electrical and Electronics Engineers (IEEE) 802.1xauthentication to an internal and/or external Remote AuthenticationDial-In User Service (RADIUS) server; an MAC authentication to aninternal and/or external RADIUS server; a built-in Dynamic HostConfiguration Protocol (DHCP) service to assign wireless client devicesIP addresses; an internal secured management interface; Layer-3forwarding; Network Address Translation (NAT) service between thewireless network and a wired network coupled to the network device; aninternal and/or external captive portal; an external management systemfor managing the network devices in the wireless network; etc.

The present disclosure may be realized in hardware, software, or acombination of hardware and software. The present disclosure may berealized in a centralized fashion in one computer system or in adistributed fashion where different elements are spread across severalinterconnected computer systems coupled to a network. A typicalcombination of hardware and software may be an access point with acomputer program that, when being loaded and executed, controls thedevice such that it carries out the methods described herein.

The present disclosure also may be embedded in non-transitory fashion ina computer-readable storage medium (e.g., a programmable circuit; asemiconductor memory such as a volatile memory such as random accessmemory “RAM,” or non-volatile memory such as read-only memory,power-backed RAM, flash memory, phase-change memory or the like; a harddisk drive; an optical disc drive; or any connector for receiving aportable memory device such as a Universal Serial Bus “USB” flashdrive), which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

As used herein, “digital device” generally includes a device that isadapted to transmit and/or receive signaling and to process informationwithin such signaling such as a station (e.g., any data processingequipment such as a computer, cellular phone, personal digitalassistant, tablet devices, etc.), an access point, data transfer devices(such as network switches, routers, controllers, etc.) or the like.

As used herein, “access point” (AP) generally refers to receiving pointsfor any known or convenient wireless access technology which may laterbecome known. Specifically, the term AP is not intended to be limited toIEEE 802.11-based APs. APs generally function as an electronic devicethat is adapted to allow wireless devices to connect to a wired networkvia various communications standards.

As used herein, the term “interconnect” or used descriptively as“interconnected” is generally defined as a communication pathwayestablished over an information-carrying medium. The “interconnect” maybe a wired interconnect, wherein the medium is a physical medium (e.g.,electrical wire, optical fiber, cable, bus traces, etc.), a wirelessinterconnect (e.g., air in combination with wireless signalingtechnology) or a combination of these technologies.

As used herein, “information” is generally defined as data, address,control, management (e.g., statistics) or any combination thereof. Fortransmission, information may be transmitted as a message, namely acollection of bits in a predetermined format. One type of message,namely a wireless message, includes a header and payload data having apredetermined number of bits of information. The wireless message may beplaced in a format as one or more packets, frames or cells.

As used herein, “wireless local area network” (WLAN) generally refers toa communications network links two or more devices using some wirelessdistribution method (for example, spread-spectrum or orthogonalfrequency-division multiplexing radio), and usually providing aconnection through an access point to the Internet; and thus, providingusers with the mobility to move around within a local coverage area andstill stay connected to the network.

As used herein, the term “mechanism” generally refers to a component ofa system or device to serve one or more functions, including but notlimited to, software components, electronic components, electricalcomponents, mechanical components, electro-mechanical components, etc.

As used herein, the term “embodiment” generally refers an embodimentthat serves to illustrate by way of example but not limitation.

It will be appreciated to those skilled in the art that the precedingexamples and embodiments are exemplary and not limiting to the scope ofthe present disclosure. It is intended that all permutations,enhancements, equivalents, and improvements thereto that are apparent tothose skilled in the art upon a reading of the specification and a studyof the drawings are included within the true spirit and scope of thepresent disclosure. It is therefore intended that the following appendedclaims include all such modifications, permutations and equivalents asfall within the true spirit and scope of the present disclosure.

While the present disclosure has been described in terms of variousembodiments, the present disclosure should not be limited to only thoseembodiments described, but can be practiced with modification andalteration within the spirit and scope of the appended claims. Likewise,where a reference to a standard is made in the present disclosure, thereference is generally made to the current version of the standard asapplicable to the disclosed technology area. However, the describedembodiments may be practiced under subsequent development of thestandard within the spirit and scope of the description and appendedclaims. The description is thus to be regarded as illustrative ratherthan limiting.

What is claimed is:
 1. A method comprising: receiving, from a clientdevice by a first network device, a wireless signal corresponding to arequest message on a first wireless communication channel; andtransmitting, by the first network device, a response messagecorresponding to the request message and addressed to the client devicevia a second network device on a second wireless communication channelor a wired communication channel.
 2. The method of claim 1, wherein theresponse message includes a signal strength level.
 3. The method ofclaim 2, wherein the signal strength level included in the responsemessage comprises a first signal strength level.
 4. The method of claim3, further comprising: deriving, by the first network device, a secondsignal strength level based on the first signal strength level, atransmit power level associated with the client device, and a transmitpower level associated with the first network device.
 5. The method ofclaim 4, wherein the signal strength level included in the responsemessage comprises the derived second signal strength level.
 6. Themethod of claim 1, wherein the response message is received via one ormore of: a wired interface to a distribution system; a first wirelessinterface to a distribution system; and a second wireless interfaceassociated with a data transmission channel of the client device.
 7. Themethod of claim 1, wherein the response message includes a designatedfield indicating that the first network device supports a channelscanning protocol.
 8. A method comprising: transmitting, by a digitaldevice, a request message on a first communication channel, the requestmessage being received by at least a first network device; switching, bythe digital device, from the first communication channel to a secondcommunication channel prior to receiving a response messagecorresponding to the request message; and receiving, from a secondnetwork device by the digital device, the response message correspondingto the request message via one of the second communication channel and athird communication channel.
 9. The method of claim 8, wherein the firstcommunication channel is a first wireless communication channel, thesecond communication channel is a second wireless communication channelused by the digital device for data frame transmissions.
 10. The methodof claim 9, wherein the response message is received via one or more of:a wired interface to a distribution system; a first wireless interfaceto a distribution system; and a second wireless interface associatedwith a data transmission channel of the digital device.
 11. The methodof claim 9, wherein the request message includes a designated fieldindicating that the digital device supports a channel scanning protocol.12. The method of claim 11, further comprising: in response to theresponse message not including the designated field, determining, by thedigital device, a first signal strength level directly from a signalstrength level associated with the received response message; and inresponse to response message including the designated field, retrieving,by the digital device, a first signal strength level from content of theresponse message; and deriving, by the digital device, a second signalstrength level based on the first signal strength level, a transmitpower level associated with the digital device, and a transmit powerlevel associated with the second network device transmitting theresponse message.
 13. The method of claim 8, further comprising:identifying the first communication channel based on a location of thedigital device.
 14. A network device comprising: a processor; a memory;a receiving mechanism operating with the processor, the receivingmechanism receives a wireless signal corresponding to a request messagefrom a client device on a first wireless communication channel; atransmitting mechanism operating with the processor, the transmittingmechanism transmits a response message corresponding to the requestmessage and addressed to the client device via a second network deviceon a second wireless communication channel or a wired communicationchannel.
 15. The network device of claim 14, wherein the responsemessage includes a signal strength level.
 16. The network device ofclaim 15, wherein the signal strength level included in the responsemessage comprises a first signal strength level.
 17. The network deviceof claim 16, further comprising: a signal deriving mechanism operatingwith the processor, the signal deriving mechanism to derive a secondsignal strength level based on the first signal strength level, atransmit power level associated with the client device, and a transmitpower level associated with the network device.
 18. The network deviceof claim 17, wherein the signal strength level included in the responsemessage comprises the derived second signal strength level.
 19. Thenetwork device of claim 14, wherein the response message is received viaone or more of: a wired interface to a distribution system; a firstwireless interface to a distribution system; and a second wirelessinterface associated with a working wireless communication channel ofthe client device.
 20. The network device of claim 14, wherein theresponse message includes a designated field indicating that the networkdevice supports a channel scanning protocol.
 21. A digital devicecomprising: a processor; a memory; a transmitting mechanism operatingwith the processor, the transmitting mechanism to transmit a requestmessage on a first wireless communication channel, the request messagebeing received by at least a first network device; a switching mechanismoperating with the processor, the switching mechanism to switch from thefirst wireless communication channel to a second wireless communicationchannel prior to receiving a response message corresponding to therequest message; and a receiving mechanism operating with the processor,the receiving mechanism to receive from a second network device theresponse message corresponding to the request message via the secondwireless communication channel or a wired communication channel.
 22. Thedigital device of claim 21, wherein the second wireless communicationchannel is used by the digital device for data frame transmissions. 23.The digital device of claim 22, wherein the response message is receivedvia one or more of: a wired interface to a distribution system; a firstwireless interface to a distribution system; and a second wirelessinterface associated with a data transmission channel of the digitaldevice.
 24. The digital device of claim 22, wherein the response messageincludes a designated field indicating that the digital device supportsa channel scanning protocol.
 25. The digital device of claim 24, whereinin response to the response message not including the designated field,the determining mechanism further to determine a first signal strengthlevel directly from a signal strength level associated with the receivedresponse message; and wherein in response to response message includingthe designated field, the digital device further comprises a signalderiving mechanism operating with the processor, the signal derivingmechanism further to: retrieve a first signal strength level fromcontent of the response message; and derive a second signal strengthlevel based on the first signal strength level, a transmit power levelassociated with the digital device, and a transmit power levelassociated with a network device transmitting the response message. 26.The digital device of claim 21, wherein the switching mechanism furtheridentifies the first communication channel based on a location of thedigital device.
 27. A non-transitory computer-readable storage mediumstoring embedded instructions that are executed by one or moremechanisms implemented within a network device to perform a plurality ofoperations comprising: receiving, from a client device, a wirelesssignal corresponding to a request message on a first wirelesscommunication channel; and transmitting a response message correspondingto the request message and addressed to the client device via a secondnetwork device on a second wireless communication channel or a wiredcommunication channel.
 28. The non-transitory computer-readable storagemedium of claim 27, wherein the response message includes a signalstrength level.
 29. The non-transitory computer-readable storage mediumof claim 27, wherein the signal strength level included in the responsemessage comprises a first signal strength level.
 30. The non-transitorycomputer-readable storage medium of claim 29, wherein the plurality ofoperations further comprises: deriving a second signal strength levelbased on the first signal strength level, a transmit power levelassociated with the client device, and a transmit power level associatedwith the network device.
 31. The non-transitory computer-readablestorage medium of claim 30, wherein the signal strength level includedin the response message comprises the derived second signal strengthlevel.
 32. The non-transitory computer-readable storage medium of claim27, wherein the response message is received via one or more of: a wiredinterface to a distribution system; a first wireless interface to adistribution system; and a second wireless interface associated with adata transmission channel of the client device.
 33. The non-transitorycomputer-readable storage medium of claim 27, wherein the responsemessage includes a designated field indicating that the first networkdevice supports a channel scanning protocol.
 34. A non-transitorycomputer-readable storage medium storing embedded instructions that areexecuted by one or more mechanisms implemented within a digital deviceto perform a plurality of operations comprising: transmitting a requestmessage on a first wireless communication channel, the request messagebeing received by at least a first network device; and switching fromthe first wireless communication channel to a second wirelesscommunication channel prior to receiving a response messagecorresponding to the request message; and receiving from a secondnetwork device the response message corresponding to the request messagevia the second communication channel or a wired communication channel.35. The non-transitory computer-readable storage medium of claim 34,wherein the second wireless communication channel is used by the digitaldevice for data frame transmissions.
 36. The non-transitorycomputer-readable storage medium of claim 35, wherein the responsemessage is received via one or more of: a wired interface to adistribution system; a first wireless interface to a distributionsystem; and a second wireless interface associated with a datatransmission channel of the digital device.
 37. The non-transitorycomputer-readable storage medium of claim 35, wherein the requestmessage includes a designated field indicating that the digital devicesupports a channel scanning protocol.
 38. The non-transitorycomputer-readable storage medium of claim 37, wherein the plurality ofoperations further comprises: in response to the response message notincluding the designated field, determining, by the digital device, afirst signal strength level directly from a signal strength levelassociated with the received response message; and in response toresponse message including the designated field, retrieving, by thedigital device, a first signal strength level from content of theresponse message; and deriving, by the digital device, a second signalstrength level based on the first signal strength level, a transmitpower level associated with the digital device, and a transmit powerlevel associated with a network device transmitting the responsemessage.
 39. The non-transitory computer-readable storage medium ofclaim 34, wherein the plurality of operations further comprises:identifying the first communication channel based on a location of thedigital device.